1. Field of the Invention
This invention relates mainly to a rotary support device, and particularly to a rotary support device suitable for use with a rotary dial apparatus for a potentiometer or the like in which a rotary shaft of the potentiometer extends into the aperture of a rotating member of the rotary dial apparatus for the adjustment of resistance value, by way of example.
2. Description oft the Prior Art
A prior art rotary dial apparatus attached to a potentiometer will hereinafter be described with reference to FIG. 1. In the FIG. 1, designates a panel for mounting a driven member such as a potentiometer 2, 3 a rotary shaft engaged with a sliding contact (not shown) of the potentiometer 2 and projecting above the panel 1 through a fixed shaft collar 4 of the potentiometer 2, 5 a rotating member or a knob of the dial apparatus, and 6 a cylindrical bed on which there are mounted the knob 5 with a rotation scale plate 18, a driven gear 13 with a rotation indicator 17, and a disc 11. The rotary shaft 3 is defined by the shaft collar 4 and a hub nut 70 so as not to be axially moved. The knob 5 has integrally provided therein a cylinder 7 for rotatably supporting the shaft 3. When the knob 5 is rotated the cylinder 7 and the shaft 3 are rotated as will be described below and hence the sliding contact in the potentiometer 2 is rotated by the shaft 3 to obtain various resistance values.
That is, the knob 5, accordingly the cylinder 7, is adapted to rotate integrally with the shaft 3 by means of screws 9 which are inserted through side bores 8 of the knob 5 to be screwed through the cylinder 7 to the shaft 3 from, for example, three directions.
Next, the rotary dial apparatus will be further described. In FIG. 1, inner teeth 10 are partially provided at the lower inner peripheral surface of the knob 5, while a disc 11 is fixedly mounted on the cylindrical bed 6 and a pinion 12 is rotatably provided on the disc 11 projecting therefrom. The pinion 12 is meshed with the inner teeth 10 of the knob 5 and also with inner teeth 14 of the driven gear 13 which is co-axially and rotatably mounted on the disc 11. A cover 15 is mounted on the bed 6 in a manner of covering the fixed portions, bed 6 and disc 11, and the rotary portions, driven gear 13 and lower part of knob 5. Thus, the rotation indicator 17 may indicate the number of rotations of the knob 5, accordingly the shaft 3, on the exterior surface of the driven gear 13 through a window 16 of the cover 15. The number of rotation of the knob 5, hence the shaft 3, and its rotated angle can be known by looking at the aforementioned indicated number of rotation and also the indication of the rotation scale plate 18 provided on the knob 5.
Further, 19 indicates a snap ring which is provided between the cylinder 7 and the disc 11 for axially fixing the cylinder 7, accordingly the knob 5, and the driven gear 13 by inserting it in the lower projecting end portion of the cylinder 7 which passes through the driven gear 13 and the disc 11. Reference numeral 20 represents a fixing plate which is engaged with the shaft collar 4 and fastened to the panel 1 by the hub nut 70 so that the panel 1 may be held between the fixing plate 20 and the potentiometer 2. One end of the fixing plate 20 is bent down and inserted into a hole 21 of the panel 1, while the other end thereof stands up and engages with a projection 22 at the inner side of the bed 6, thus the rotation of the bed 6 being limited or stopped.
With the prior art apparatus as mentioned above, if the knob 5, cylinder 7, driven gear 13, disc 11 and the like are improperly centered or inaccurately finished when assembled the shaft 3 will not smoothly rotate or sometimes will not be rotatable so that the apparatus may be unusable and hence not economical. Accordingly, in such a case, temporary procedures are taken such as to enlarge the axial bores 24 and 24' of the knob 5 and cylinder 7, respectively, for manually adjusting the fastening condition of the screws 9 from three directions or to incline the bed 6 relative to the panel 1. Thus, the proper axial engagements of the shaft 3 and the cylinder 7 with the aforesaid bores 24' and 24 were barely achieved so as to make the shaft 3 rotatable and the number of defective members was decreased or made minimum. However, the above procedures were not radical and from technical and economical points of view it was unreasonable to enhance the accuracy of finishing of each member.